In order to obtain electric contact in the area of the screw connection in such devices, it has been customary to remove part of the surface in the areas around the boreholes or to take measures, in applying the protective coating, to assure that the protective layer is not applied in such areas. This, however, always requires an additional operation during manufacture, which increases costs. Furthermore, such screw connections must be tightened exactly and not be moved later. But this cannot always be guaranteed, as in the case of modifications in a switchboard where bar rails are added later or attached to the body of the console elsewhere.
As shown by German Utility Patent No. 8,001,886, a threaded component can be connected in an electrically conductive manner to a board-shaped component by providing the nut with teeth or the like on the side which faces the component such that the teeth penetrate the surface layer when the nut is tightened. This establishes direct electrically-conductive connection with the component. However, such nuts of the prior art do not permit a connection of two components in a manner permitting electrical conduction if both components are coated with a substantially non-conductive coating.
This could be achieved if the head of the screw of a screw connection were also provided with teeth or the like on its side facing the component. However, this has the disadvantage that the surface layer would be destroyed in the area of such head. Then, in event of alterations or changes in position of the screw connections, the damaged areas of the surface layers of both components would be visible.